ABS brake clicking noise in engine bay

[sdsisuzu]

I have a '95 Rodeo with 104,000 miles that I bought when it had 100,00 on it, so I don't have any service records.

When I come to a stop, when using my brake at low speeds the brake pedal pulsates and it feels like the rear ABS is working but I'm also hearing a rapid clicking noise coming from the right side of the engine bay (under the hood). If I let off the brake pedal, it stops and if I reaply the brakes slowly it doesn't happen again.

It seems to be happening just as I am coming to a stop.

Just replaced my rear calipers and pads. This also happened before I replace those.

Any ideas?